The present invention relates to the field of nanostructured polymer-blend composite materials, particular photonic polymer-blend structures having tunable optical and mechanical properties.
Nanostructured polymer-blend or polymer-inorganic composite materials are the subject of intense and wide-spread interest as researchers pursue next-generation xe2x80x9csoft-materialxe2x80x9d species with tunable properties. In particular, there continues to be strong interest in the complex mechanics of viscoelastic systems, droplet coalescence, behavior of polymer blends in shear fields, as well as in electrospinning of polymer nanofibers. There is limited literature on fabrication of semiconductor structures with similar functionality. The lithographic fabrication techniques are expensive, time-consuming, and require specialized hardware and expertise. Further, cryogenic temperatures are required to observe the desired optical coupling between components in the composite structure. The understanding of the fundamental polymer physics of these systems is crucial to the development of advanced materials and processing techniques involving polymer blends at micro- and nanoscopic length scales. Furthermore, while there is a great deal of interest currently in the field of xe2x80x9cmicrophotonicsxe2x80x9d, or manipulation, both in spatial and frequency dimensions, of photons for electro-optic device enhancement, wavelength division multiplexing applications and optical computing, there exists few new device strategies for overcoming the difficulties of highly specific frequency response/transmission characteristics, and spatial localization at or near diffraction-limited resolution. Fiber-optic technology, for example, is widely used for xe2x80x9cphoton conduitsxe2x80x9d but is selective in terms of frequency transmission characteristics- all possible frequencies are transmitted through the fiber that are permitted by the optical material. In the case of photonics or photonic-bandgap structures, only specific frequencies are allowed to propagate. The photonic polymer-blend structures of the present invention are similar in that regard, but allow for a multiplicity of structural architectures that are not possible with conventional photonics bandgap crystals.
Accordingly, it is an object of the present invention to provide two- and three-dimensional photonic polymer-blend structures having a variety of architectures.
It is another object of the present invention to provide photonic polymer-blend structures having tunable optical and mechanical properties.
It is a further object of the present invention to provide photonic polymer-blend structures having desired architectures formed by the sequential attachment of polymer-blend spherical microparticles partially merged with one another in a robust inter-particle bond having tunable bond lengths.
Further and other objects of the present invention will become apparent from the description contained herein.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a photonic polymer-blend structure having tunable optical and mechanical properties. The structure comprises monomer units of spherical microparticles of a polymer-blend material wherein the microparticles have surfaces partially merged with one another in a robust inter-particle bond having a tunable inter-particle separation. The polymer-blend spherical microparticles of the photonic polymer-blend structure are sequentially attached to one another in a desired and programmable architecture.
In accordance with another aspect of the present invention, other objects are achieved by a method for making photonic polymer-blend structures having tunable optical and mechanical properties. The method comprising the steps of a) providing an aqueous polymer-blend solution comprising a relative mass fraction of polyethylene glycol and polyvinyl alcohol wherein the solution has a sufficient water and polymer blend ratio to form polymer-blend spherical microparticles having specific properties and morphology to enable the microparticles to partially merge in a sequential attachment with one another to form an inter-particle bond wherein the specific properties and morphology of the microparticles tune the inter-particle separation of the inter-particle bond and wherein the specific properties and morphology of the spherical microparticles produce a desired photonic polymer-blend structure having a desired architecture. The method of the present invention further comprising b) injecting the aqueous polymer-blend solution into a particle focusing device at a sufficient rate to form individual droplets of solution; c) controlling the parameters of the particle focusing device to allow the droplets to be spatially focused and guided through the particle focusing device to form spherical microparticles partially merged in a sequential attachment in an inter-particle bond with one another and having a tuned inter-particle separation; and d) depositing the spherical microparticles in a precise placement on a collection device forming a desired architecture of the photonic polymer-blend structure.